USE=debug emerge -av zynaddsubfx

These are the packages that would be merged, in order:

Calculating dependencies... done!
[ebuild     U ] media-sound/zynaddsubfx-20070707 [2.2.1-r8] USE="alsa debug%* jack jackmidi lash mmx%* -oss" 0 kB [2] 

Total: 1 package (1 upgrade), Size of downloads: 0 kB
Portage overlays:
 [1] /usr/local/portage/perso
 [2] /usr/local/portage/proaudio

Would you like to merge these packages? [Yes/No] y
>>> Verifying ebuild Manifests...

>>> Emerging (1 of 1) media-sound/zynaddsubfx-20070707 to /
 * zynaddsubfx-presets-0.1.tar.bz2 MD5 ;-) ...                                                                                                   [ ok ]
 * zynaddsubfx-presets-0.1.tar.bz2 RMD160 ;-) ...                                                                                                [ ok ]
 * zynaddsubfx-presets-0.1.tar.bz2 SHA1 ;-) ...                                                                                                  [ ok ]
 * zynaddsubfx-presets-0.1.tar.bz2 SHA256 ;-) ...                                                                                                [ ok ]
 * zynaddsubfx-presets-0.1.tar.bz2 size ;-) ...                                                                                                  [ ok ]
 * ZynAddSubFX-20070707.tar.bz2 MD5 ;-) ...                                                                                                      [ ok ]
 * ZynAddSubFX-20070707.tar.bz2 RMD160 ;-) ...                                                                                                   [ ok ]
 * ZynAddSubFX-20070707.tar.bz2 SHA1 ;-) ...                                                                                                     [ ok ]
 * ZynAddSubFX-20070707.tar.bz2 SHA256 ;-) ...                                                                                                   [ ok ]
 * ZynAddSubFX-20070707.tar.bz2 size ;-) ...                                                                                                     [ ok ]
 * checking ebuild checksums ;-) ...                                                                                                             [ ok ]
 * checking auxfile checksums ;-) ...                                                                                                            [ ok ]
 * checking miscfile checksums ;-) ...                                                                                                           [ ok ]
 * checking ZynAddSubFX-20070707.tar.bz2 ;-) ...                                                                                                 [ ok ]
 * checking zynaddsubfx-presets-0.1.tar.bz2 ;-) ...                                                                                              [ ok ]
 * jackmidi support [OK]
>>> Unpacking source...
>>> Unpacking ZynAddSubFX-20070707.tar.bz2 to /var/tmp/portage/media-sound/zynaddsubfx-20070707/work
>>> Unpacking zynaddsubfx-presets-0.1.tar.bz2 to /var/tmp/portage/media-sound/zynaddsubfx-20070707/work/ZynAddSubFX-20070707
>>> Source unpacked.
>>> Compiling source in /var/tmp/portage/media-sound/zynaddsubfx-20070707/work/ZynAddSubFX-20070707 ...
make -C UI all
make[1]: Entering directory `/var/tmp/portage/media-sound/zynaddsubfx-20070707/work/ZynAddSubFX-20070707/src/UI'
fluid -c WidgetPDial.fl
make[1]: *** No rule to make target `WidgetPDial.h', needed by `WidgetPDial.o'.  Stop.
make[1]: *** Waiting for unfinished jobs....
make[1]: Leaving directory `/var/tmp/portage/media-sound/zynaddsubfx-20070707/work/ZynAddSubFX-20070707/src/UI'
make: *** [all] Error 2

!!! ERROR: media-sound/zynaddsubfx-20070707 failed.
Call stack:
  ebuild.sh, line 1621:   Called dyn_compile
  ebuild.sh, line 973:   Called qa_call 'src_compile'
  ebuild.sh, line 44:   Called src_compile
  zynaddsubfx-20070707.ebuild, line 79:   Called die

!!! make failed with this options: FFTW_VERSION=3 ASM_F2I=YES LINUX_MIDIIN=ALSA LINUX_AUDIOOUT=JACK LINUX_USE_LASH=YES LINUX_USE_JACKMIDI=YES
!!! If you need support, post the topmost build error, and the call stack if relevant.
!!! A complete build log is located at '/var/tmp/portage/media-sound/zynaddsubfx-20070707/temp/build.log'.

This ebuild used the following eclasses from overlays:

  /usr/local/portage/proaudio/eclass/jackmidi.eclass

!!! This ebuild is from an overlay: '/usr/local/portage/proaudio'